Light transmission cables for telecommunications work typically include a thin fiber of glass enclosed within a sheath of tough plastic material for protection. At a receiving end of the fiber, there is often formed a globular lens portion for focusing upon an electronic device which converts a light signal into an electrical signal. Such lens portion should be precisely formed from the glass, closely concentrix with the axis of the fiber and without bubbles or stress cracks.
A typical method of forming the lens has been to suspend a cable vertically and to horizontally reciprocate an end of the fiber in and out of a flame produced by a gas jet. As an end portion was treated, the end was repeatedly measured until a desired globular portion was completely formed. However, the globe sometimes grew too large or lateral bending occurred, due inter alia, to non-uniform heating and unilateral thrusting from the gas jet. As a result, defective globe portions often had to be removed and the process repeated until proper lenses were formed. Consequently, there is a need for more positive retention of the work combined with steady rotation thereof to obtain better distribution of heat and forces upon a glass end being treated. Such retention and rotation of workpieces is often provided by a class of devices referred to in the art as "chucks" which are rotated in conventional apparatus.
Conventional chucks generally include gears and/or cams which provide great mechanical advantage in compressing and thereby securing a workpiece for rotation in a lathe or a drill press. However, glass fibers should be more delicately handled and compression thereof more carefully controlled. Moreover, conventional chucks are not usually equipped to accommodate a flexible length of cable for rotation of an end portion of fiber. Even those chucks which may be adapted to the described procedure for forming lenses, require tedious steps to carefully mount and demount a cable, and such steps are time consuming.